"This in itself is a huge advance," Blau said of the software. "Until now it's been pretty impossible to do these studies without spending half a year or more manually scoring pictures or movies of cells in culture. Now we can figure out exactly how the cells divide and move, who begets who. As a result we can begin to study all types of variables."
After studying the dynamics of the muscle stem cells' division and dying, the researchers began to study specific aspects of their biology. They found that the cells grown on the softer surface were less likely than those grown on the harder surfaces to express a gene associated with differentiation called myogenin. They were also as able as freshly isolated muscle stem cells to contribute to the development of leg muscles when transplanted into recipient mice.
"Testing their function in animals like this is extremely important," said Blau. "It's really the only way to confirm their 'stemness.'"
To prove definitively that the stem cells were self-renewing, Gilbert and Blau turned to a "doublet" experiment. In this test, Gilbert allowed just one cell to divide just one time, resulting in two daughter cells. There are three potential combinations for these resulting doublets: two stem cells, one stem cell and one progenitor cell, or two progenitor cells. The first two represent self-renewal; the last does not. (A progenitor cell is one that can go on to differentiate into
|Contact: Krista Conger|
Stanford University Medical Center